There have been proposed inkjet printing devices capable of executing a bleed suppression process for reducing the likelihood of black ink bleeding into neighboring color pixels. In this process, the printing device finds pixels that meet a prescribed condition, such as having a color pixel on the periphery thereof, sets these pixels as candidate pixels for bleed suppression, and substitutes a combination of color ink in a plurality of colors for the black ink of these target pixels. Thus, the printing device prints the black color of these target pixels without using black ink.
When checking each pixel of an image to determine whether the pixel needs to be processed to suppress bleeding, the printing device must reference not only the target pixel being checked, but also the peripheral pixels within a prescribed range of the target pixel. Since it is inefficient to reference image data stored on a hard disk drive or other storage medium directly because a considerable amount of time is required to read such image data, image data for the image to be printed is read into a band buffer capable of storing five lines worth of data, for example, and a process is performed on the data stored in the band buffer to determine which pixels must be subjected to the bleed suppression process.